1. Field of the Invention
The present invention relates to a fuel injection control apparatus for a multi-fuel engine. More particularly, the present invention relates to a fuel injection control apparatus for a multi-fuel engine, which is capable of setting, without preparing a basic injection map which determines an injection quantity of fuel for a plurality of operation state of the engine for every alcohol concentration, an optimum fuel injection quantity based on only one basic injection map, irrespective of measured alcohol concentration.
2. Description of the Background Art
Recently, from a viewpoint of protecting an environment, as one of substitute fuels for fossil fuels, an alcohol fuel is considered as a promising fuel, and a vehicle which is capable of operating using an alcohol mixed fuel produced by mixing alcohol and gasoline besides gasoline, e.g. a Flexible Fuel Vehicle (FFV) has been developed.
The alcohol mixed fuel differs from fuel consisting of 100% of gasoline with respect to a heat value and an evaporation characteristic. At the same time, the alcohol mixed fuels differ from each other in characteristics depending on alcohol concentration indicative of a mixing rate of alcohol relative to gasoline.
Accordingly, when an alcohol mixed fuel is used in an engine which premises on the use of fuel consisting of 100% of gasoline, a control air/fuel ratio falls outside a theoretical air/fuel ratio. As a result, there may be a possibility that contents of an exhaust are changed or drivability of the vehicle is changed.
In order to overcome such drawbacks of using alcohol mixed fuels, the Japanese patent document JP-A-2004-2934911 discloses a system for performing correction of fuel injection quantity corresponding to alcohol concentration which is corrected to a value in the vicinity of approximately intermediate concentration.
In the system of the related art, disclosed in the Japanese patent document JP-A-2004-2934911, it is difficult to correlate a fuel injection quantity to an actual change of alcohol concentration. At the same time, even when a fuel injection map which determines a correlation between an operation state of an engine and a fuel injection quantity is provided, it is necessary to provide the fuel injection map for every alcohol concentration of fuel. Hence, it is necessary to update all fuel injection maps every time the specification of the engine is changed.
The present invention has been made to overcome such drawbacks of the existing fuel injection system. Accordingly, it is one of the objects of the present invention to provide an apparatus and a method of a fuel injection control for a multi-fuel engine which can overcome the above-mentioned drawbacks of the prior art, and can acquire a proper fuel injection quantity using only one basic injection map irrespective of alcohol concentration of fuel.